Weighing 2.9 tons and traveling 4.8 miles per second, this pile of old batteries is now the heaviest piece of debris thrown overboard from the International Space Station.
The pallet is loaded with nickel-hydrogen batteries and will remain in low Earth orbit for the next two to four years “before being harmlessly burned in the atmosphere,” according to a NASA. pronunciationSpaceFlightNow reports that the pallet is “the most massive object ever thrown from the outpost into orbit”.
NASA spokesman Leah Cheshier confirmed this to be the case.
“The External Pallet was the largest object – by mass – ever dropped from the International Space Station at 2.9 tons, more than twice the mass of the Early Ammonia Servicing System tank used during the STS-118 mission. was thrown overboard in 2007 by spacewalker Clay Anderson. Cheshier wrote in an email.
NASA’s ballistic officers “indicate there is no threat” of the pallet colliding with other space objects, but “this item, like all, will be tracked by US Space Command,” she added.
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The original plan was not to dispose of the pallet in this way. The launch failure From a Soyuz rocket in 2018, in which NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin were forced to make an emergency landing in the Kazakh steppe, disrupted the spacewalk schedule, leading to the remaining pallet.
NASA’s spacewalk on February 1, 2021, involving astronauts Mike Hopkins and Victor Glover, was remarkable in that it culminated in a four-year effort to upgrade the space station’s batteries. These batteries store energy collected by solar panels, but in 2011 NASA decided to switch from nickel-hydrogen batteries to lithium-ion batteries. Production of these batteries started in 2014 and the process to exchange them started in 2016.
This effort required four supply missions from Japan’s H-II Transfer Vehicle (HTV) cargo spacecraft, 13 different astronauts and 14 spacewalks, replacing 48 nickel-hydrogen batteries with 24 lithium-ion batteries.
Normally, the old batteries would be put in an HTV and thrown overboard from the ISS, and the items would usually burn out when they got back in. But the failed launch of the Soyuz disrupted the pattern of spacewalks and the intended schedule so that an HTV freighter left the station without a battery pallet in late 2018, according to SpaceFlightNow. The battery replacement mission continued and HTVs continued to leave the station with pallets, but now with an extra permanently attached to the station. With the mission over and no more HTVs coming (at least none of the old design – they’re being replaced by the HTV-X cargo spacecraft), mission planners had to jettison the pallet themselves.
So that’s what they did on Thursday, March 11, when mission controllers in Houston used the Canadarm2 robotic arm to “release an external pallet of old nickel-hydrogen batteries into orbit”, according to to NASA. The object was released about 427 km above the Earth’s surface.
“In the past, throwing things off the ISS wasn’t that bad because there were very few satellites were under it [at altitudes below 250 miles (400 km)] Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics, explained in an email.Not so with a bunch of cubesats and with recently launched Starlinks while raising the track. So I’m worried. “
To which he added: “I don’t immediately see what they could have done other than flying a whole extra HTV mission to get rid of it. “
According to the European Space Agency, around 34,000 objects larger than 10 cm are currently in orbit, in addition to millions of smaller objects, such as tools and parts of spacecraft. The volume of objects in the space, both functional and non-functional, is steadily increasing, giving rise to concern possible collisions and even more orbital debris.
This post has been updated with comments from Jonathan McDowell.